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PhotogiHphic 

Sciences 
Corporation 


23  WEST  MAIN  ST(;EET 

WEBSTER,  N.Y.  14580 

(716)  87':-4503 


CIHM/ICMH 

Microfiche 

Series. 


CfHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  canadien  de  microreproductions  historlques 


\ 


^ 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibliographiques 


The  Institute  has  attempted  to  obtain  the  best 
original  copy  available  for  filming.  Features  of  tJiis 
oopv  which  mav  be  bibliographicallv  unique, 
which  may  alter  any  of  the  images  in  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checked  below. 


Coloured  covers/ 
Couverture  de  couleur 


L'Institut  a  microfilm^  le  meilleur  exemplaire 
qui!  lui  a  ete  possible  de  se  procurer.  Les  details 
dn  cet  exemplaire  qui  sont  peut-dtre  uniques  du 
point  de  vue  bibliographique,  qui  peuvent  modifier 
une  image  reproduite,  ou  qui  peuvent  exiger  une 
modification  dans  la  m^thode  normale  de  filmage 
sont  indiqu^s  ci-dessous. 


D 


Coloured  pages/ 
Pages  de  couleur 


Th« 
to  tt\ 


The 
posa 
of  tH 
filmi 


n 


D 


Covers  damaged/ 
Couverture  endommagee 


Covers  restored  and/or  laminated/ 


I I    Couvert  (r«  restaur^e  et/ou  pelliculee 


Co  r»^  ti.le  missing/ 

Le  tit.e  de  couverture  manque 


□    Pages  damaged/ 
Pages  endommag^es 


□    Pages  restored  and/or  laminated/ 
Pages  restaurees  et/ou  pelliculees 


E 


Pageo  discoloured,  stained  or  foxed/ 
Pages  d^coloraes,  tachet^es  ou  piquees 


Origi 
bagi 
the  I 
sion 
othe 
first 
sion 
or  ill 


I      I    Coloured  maps/ 


D 
D 
D 
D 


D 


Cartes  gAographiques  en  couleur 

Coloured  ink  (i.e.  other  than  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noire) 


Coloured  plates  and/or  illustrations/ 
Planches  et/ou  illustrations  en  couleur 

Bound  with  other  material/ 
R&li^  avec  d'autre«  documents 


Tight  binding  may  causa  shadows  or  distortion 
along  interior  margin/ 

Lareliure  serree  peut  causer  de  I'ombre  ou  de  la 
distorsiorr  lo  long  de  la  marge  interirjura 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanchas  ajouties 
lors  d'une  restauration  apparaissent  dans  le  texte, 
mais,  lorsque  cela  6tait  possible,  ces  pages  n'ont 
pas  6x6  filmdes. 


□Pages  detached/ 
Pages  ddtachees 

["Tj    Showthrough/ 
I I    Transparence 

pn    Quality  of  print  varies/ 


D 


D 


Quality  inigale  de  I'impresaion 


Includes  supplementary  material/ 
Comprend  du  materiel  supplementaire 


□    Only  edit'on  available/ 
Seule 


The 
shall 
TINl 
whic 

Map 
diffe 
entir 
begii 
right 
raqu 
matt 


Edition  disponible 


Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc..  have  been  refilmed  to 
ensure  the  best  possible  image/ 
Les  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc..  cnt  6t6  fiim^es  d  nouveau  de  facon  a 
obtenir  la  meilleure  image  possible. 


□ 


Additional  comments:/ 
Commentaires  suppl^mentaires: 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  est  filmd  au  taux  de  reduction  indiqui  ci-de^r.cus. 


10X 

14X 

18X 

22X 

26X 

30X 

L« 

1 

1     . 
j   i 

i 

1     1 
1 

12X 


16X 


20X 


24X 


28X 


32X 


** 


lils 

iu 

difier 

jne 

lage 


The  copy  filmed  hare  has  b««n  raproducad  thanks 
to  tha  ganarosity  of: 

Library, 

Geological  Survey  of  Canada 

Tha  imagaa  appaaring  hara  ara  tha  baat  quality 
possibia  considaring  tha  condition  and  lagibility 
of  tha  original  copy  and  in  kaaping  with  tha 
filming  contract  spacificationa. 


L'axamplaira  filmA  fut  raproduit  grica  h  la 
gAnirosit*  da: 

Biblioth^ue, 

Commission  G6ologique  du  Canada 

Laa  imagaa  suivantaa  ont  Ati  raproduitaa  avac  la 
piua  grand  soin,  compta  tanu  da  la  condition  at 
da  la  nattat*  da  l'axamplaira  filmi,  at  an 
conformity  avac  laa  conditions  du  contrat  da 
fiimagv. 


Original  copias  in  printad  papar  covars  ara  fiimad 
beginning  with  tha  front  eovar  and  ending  on 
tha  last  page  with  a  printad  or  illustrated  impres- 
sion, or  tha  ba^ic  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  imprea- 
sion,  and  arvding  on  the  last  page  with  a  printad 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  —*•( meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 


Las  exemplairaa  originaiix  dont  la  ccuverture  sn 
papier  eat  imprim^  sont  filmte  an  commenqant 
par  le  premier  plat  at  an  terminant  soit  par  la 
darniAre  page  qui  comports  une  ampreinte 
d'Impreasion  ou  d'illustratton,  soit  par  le  second 
plat,  salon  la  cas.  Tous  las  autres  axamplairas 
originbux  sont  filmte  an  commancant  par  la 
premiere  page  qui  comporte  une  ampreinte 
d'impresaion  ou  d'illustration  at  an  terminant  par 
la  derniire  page  qui  comporte  une  telle 
empreinte. 

Un  dea  symbolea  suivants  apparaitra  sur  la 
damiire  image  de  cheque  microfiche,  selon  le 
caa:  le  symbols  — *>  signifie  "A  SUIVRE",  ie 
symbolc  V  signifie  "FIN". 


Mapa,  piatea.  charts,  etc.,  may  be  filmed  at 
different  reduction  ratioa.  Thoae  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hanr*  corner,  left  to 
right  and  top  to  bottom,  aa  many  f/ames  as 
required.  The  following  diagrams  illustrate  the 
method: 


Lea  cartea.  pianchaa.  tableaux,  etc.,  peuvent  atre 
filmte  ^  dea  taux  de  reduction  diff  Arents. 
Lorsqua  le  document  est  trop  grand  pour  dtre 
reproduit  en  un  seul  cliche,  il  est  filmi  d  partir 
de  i'angie  supArieur  gauche,  de  gauche  ii  droite. 
et  da  haut  en  baa.  an  prenant  ie  nombre 
d'imagea  n^cassaira.  Las  diagram  mas  suivants 
illustrent  la  mithode. 


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CROSSING  NEW  HAMPSHIRE  AND  VERMONT. 


By  PROin.  C.  H.  HXrOBiCOCns.. 


CONCORD,    N.    H.: 

PRINTED   MY   THE   REPUBLICAN   PRESS  ASSOCIATION. 

1884. 


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I 


NEW   HAMPSHIRE      BY      C  H.  HITCHCOCK . 


RE      BY      C    H    HITCHCOCK 


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DESCRIPTION 


O  V 


Geological  Sections 


i 


CROSSING  NEW  HAMPSHIRE  AND  VERMONT. 


By   P>R,Oii\  C.  H.  HITCHCOCK. 


CONCORD,     N.     H.: 

PRINTED   BY   THE   REPUBLICAN   PRESS  ASSOCIATION. 

18  8  4. 


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V 


GEOLOGICAL  SECTIONS  OF  NKW  HAMPSHIRE 
AND  VERMOiNT. 


^ 


»Six  years  ago  the  final  report  \\\i<n\  the  Geology  of  New 
Hampshire  was  pnblislied  by  order  of  the  legislature.  Since 
that  time  the  author  of  this  paper,  who  held  the  ofHce  of  state 
geologist,  has  had  occasion  to  revise  the  general  sections  de- 
scribed in  his  report,  and  also  to  extend  tlietn  through  Vermont. 
Specimens  to  the  number  of  three  thousand  illustrate  them  upon 
the  shelves  of  the  museum  of  the  New  Hampshire  College  of 
Agriculture  and  the  Mechanic  Arts,  where  colored  profiles  will 
also  be  found  upon  a  liberal  scale.  The  profiles  are  forty  feet 
long,  extending  the  entire  length  of  the  room  upon  the  back 
side  of  the  case  and  between  the  shelves.  The  different  series 
of  strata  are  represented  by  colors,  and  the  numbers  printed 
upon  the  profiles  correspond  to  those  pasted  upon  the  specimens 
directly  in  front.  Thirteen  slielves  are  arranged  in  order,  one 
over  another,  from  the  floor  to  the  ceiling.  Care  is  taken  not 
to  impede  the  view  of  the  colored  profiles  by  braces  or  railing 
in  the  gallery,  so  that  the  visitor  may  examine  the  whole  series 
either  in  detail  or  at  a  glance.  These  shelves  are  a  truthful 
re[)resentation  of  nature.  Three  thousand  ledges  are  represent- 
ed in  their  proper  geographical  order,  and  by  proper  study  any 
one  can  classify  the  several  groups  without  the  labor  of  travel- 
linsi  over  the  country.  More  or  less  of  theory  is  given  in  the 
profiles,  and  the  author  is  desirous  of  iiaving  his  views  submitted 
to  criticism.  The  conclusions  derived  from  the  study  of  these 
sections  have  been  embodied  in  the  reports  upon  the  geology  of 


both  New  Hampsliire  and  Vermont ;  l)iit  a  resiirvev  of  them  has 
eimbled  me  to  convct  doubtful  points,  to  confirm  trutliful  rep- 
resentations, to  change  the  published  section  lines  where  im- 
provements were  i)ossible,  to  take  advantage  of  observations 
made  by  other  observers,  ami  to  present  a  connected  view  of 
what  lias  l)een  learned  concernin<>;  the  <;eological  succession  in 
the  two  states,  A  knowledge  of  this  territory  furnishes  the  key 
to  unlock  the  mysteries  of  New  England  geology,  as  well  as 
th.it  of  the  whole  of  the  middle  -ection  of  the  Atlantic  <>-eo(rrai)h- 
ical  area.  In  the  same  room  at  Hanover  may  be  seen  a  large 
colored  ge()h)gical  relief-map  of  New  Hampshire  uiM)n  the 
scale  of  one  mile  to  the  inch  horizontally,  and  one  thousand  feet 
to  the  inch  vertically.  Portions  of  Vermont  are  also  shown, 
and  it  is  our  i)urpose  to  show  the  whole  of  that  state,  as  well  as 
a  part  of  Maine,  upon  the  same  platform.  These  relief  maps 
and  half  of  the  specimens  illustrating  the  Vermont  sections 
belong  to  Dartmouth  college. 

A  similar  collection  of  specimens  is  on  exhibition  at  the  rooms 
of  the  American  JNIuseum  of  Natural  History  in  New  York, 
together  with  the  same  large  relief-map  of  New  Hampshire, 
colored  t<>  correspond  with  the  published  geological  map 
of  New  Hampshire.  A  special  description  of  that  has  been 
printed  in  Bulletin  No.  8  of  the  {)ublications  of  that  institution. 
At  the  normal  school  in  Plymouth  there  is  a  similar  exhii)itiou 
of  the  New  Hampshire  i)art  of  this  collection,  but  no  attempt 
has  l)een  made  there  to  grouj)  them  in  order  upon  shelves  ac- 
companied by  the  colored  illustrative  protiles. 

Our  object  in  preparing  this  ski-tch  is  to  so  record  the  most 
important  facts  connected  with  our  explorations,  that  those  who 
visit  Hanover  may  have  the  opportunity  to  verify  our  conclu- 
sions for  themselves  by  studying  the  specimens,  both  lithologi- 
cally  and  stratigraphically.  The  work  of  exploration  was  under- 
taken with  the  determination  to  discover  what  the  rocks  them- 
selves taught,  and  not  in  the  interest  of  any  theory.  Hence 
students  may  rely  upon  the  truthfulness  of  all  the  representa- 
tions. The  specimens  come  from  ledges  in  the  localities  indi- 
cated, and  the  positions  of  the  strata  are  stated  according  to 
our  best  judgment  from  personal  observation.  If  there  is  ever 
any  want  of  symmetry  in  the  folds,  if  one  side  of  an  axis  seems 


tu 


1  * 


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& 


to  possess  an  fXiiiiSiTutod  tliicknt'ss,  it  is  bt'caiiHe  all  the  facts 
needed  for  full  delineation  are  not  known.  I'uin.s  are  taken  not 
to  represent  curves  and  fividts  except  those  whose  existence  is 
un(|Ui'stional»le.  Ilencu'  tiie  in(|uii'cr  can  utilize  the  ten  veais  of 
field  and  otilee  work  embodied  in  tlieho  colleetions  nearly  as  well 
as  if  he  had  jjone  over  tiie  <rronnd  iiiniself.  IU>  will  also  under- 
stand for  iiiniself  tin,'  localities  where  supplementary  observa- 
tions are  needed. 

About  00,000  feet  thickness  of  strata  occur  over  this  territory. 
As  they  have  not  been  particularly  investi<fated  elsewhere,  it 
follows  that  many  <»roups  must  exist  not  ^eneniily  recognized, 
and  peculiar  designations  must  be  employed  which  will  be  per- 
plexing. To  assist  the  incpiirer,  I  will,  at  first,  present  a  few 
general  conclusions,  based  upon  a  terminology  readily  under- 
stood, reserving  the  fuller  details  of  our  scheme  of  classification 
and  structure  for  the  sequel,  to  be  fully  a[)preciated  only  by  a 
painstaking  exanjinution  of  the  larger  profiles  and  specimens  in 
the  cases. 

It  should  also  be  borne  in  mind  that  our  various  grou|)s  or 
formations  are  classified  according  to  stratigraphical  reasons, 
and  not  lithology.  liithological  names  may  be  used  for  conven- 
ience, or  so  as  to  avoid  the  multiplication  of  local  designations. 
A  lithological  similarity  is  useful  in  tracing  a  formation  from 
farm  to  farm,  or  town  to  town,  throughout  a  county,  or  to  iden- 
tify the  opposite  side  of  a  synclinal  basin  or  :Miticliiial  ridge. 
Furthermore,  unlike  rocks  are  never  assumed  to  be  identical.  If 
a  honihli'iide  schist  and  clay  slate  dip  toward  each  other,  tiiey 
are  assumed  to  be  of  different  age  and  separated  by  ii  fault  or 
unconformity.  All  the  igneous  rocks  of  our  field  are  held  to  be 
truly  eiiiptive.  and  are  devoid  of  marks  of  stratilicatioii.  If  a 
granitic  rock  siiows  foliation,  it  is  classed  among  the  gneisses. 

Tlie  pul)lished  sections  accompanying  this  [)aperhave  the  hor- 
izontal scale  of  ,(„,,',, I, II'  ''"*!  t''*-'  vertical  of  about  icoVod-  '^'^^^y 
are  arranged  geograpiiicaliy  correct  with  reference  to  each  other, 
and  the  meridians  and  longitude  are  drawn  as  upon  a  map.  In 
some  cases  the  extreme  east  or  west  ends  of  tlie  sections  are  not 
rei)resente(l.  Tlu'  base  line  of  all  the  sections  is  ir).')0  feet 
below  tide-water.  Twelve  vai'iatioiis  of  lines,  dots,  and  dashes 
indicate  as  many  groups  of  rocks  upon  wliich  our  pri'uary  con- 


cliisions  art!  based.  Tliev  .'ifo, —  1 .  *Xini!;;irji  j^ioiip.  -J.  I  ppor 
Canibro-SiliiriMii  slates  uod  scliists.  M.  Camhro-Siliiriuii  liino- 
stoiH's.  4.  '!'lic  C'omicoticiit  Valley  mica  schists,  <|iiartzit('8, 
ot(!.,  n-fcrii'd  a)  llie  ('oils  <j;r()up  in  the  New  Ilaiiipsliire  reports, 
and  the  ealciferons  mica  schists  of  the  re|)orts  of  lioth  statea. 
.0.  Potsfhim  sandstone.  (1.  Clay  slates  an(',  arjrillitic  and  other 
schists,  supposed  to  lie  of  Ciimbiian  njjc  Of  these,  the  "(Jeor- 
gia  slates"  of  the  N'ernioiit  report  conttiin  the  (Hoielhis  and  Jn- 
gcliiKi ;  the  ()thers  have  not  yet  yielded  any  (»r<ianiMn.  7.  Mica 
schist  of  eastern  New  Hampshire,  a  part  of  the  *'  Hoekiii<j;h!iin 
group"  of  the  re|)ort.  M.  Iluronian.  inclndinji-  the  chi(»ritic, 
ar<;illitic.  dioritic  schists,  (pnirt/ites.  -ind  protojjenes  thinking 
the  (Jreen  IMountains.  :uid  adjoiiiiiiij,  the  (  onnccticut  liver,  or 
the  rocks  UHiially  refern-d  to  this  yroiip  l>y  authors  ;  also  the 
'•  Merrinnick  <>'roiip,"  •' Ferriiiiiiioiis  slates.'"  ••  Ki-arsar^e  u,i()up," 
and  part  of  the  •"  Hockin^hain  ^roiip  "  of  tlii'  New  llamiishire 
report.  !>.  Montalhan  rocks,  as  delined  in  the  New  Hampshire 
report,  iiicludinif  the  schists  holdin<i-  the  co.'irse  <iranite  veins 
carryiiiii'  niercliantahle  mica.  lo.  Ordinary  <rneiss,  inclnding  the 
"(Jreen  ."Mountain."  '•  Lake  U'iiiiiipiseo<>-ee.  and  ••  IJethlehem" 
varieties  of  the  reports.  11.  Poiphyrilic  <>iieiss.  To  these 
may  he  added  another  distinction  f<»r  tiie  uiistratilied  rocks,  ia 
which   are  I'luhraced  granite,  syenite,  and  [lorphyiy. 


Till:     <  A>llll{()-S11,11!1AX. 

Trohahly  the  whole  of  this  division  of  tlii'  Paleozoic  rocks 
occurs  in  the  Champlain  valh'y.  Sections  I  toX'H  display  amass 
of  green  hydro-mica  ^(•lli^ts  overlying  the  fossiliferoiis  limestones 
of  this  series,  and  ma_\ .  perhaps,  represent  the  Loraiiu' slates  of 
Ni'w  York.  On  our  section  lines  the  'I'renton  is  wanting  in 
immediate  contiguity  to  these  schists,  so  that  the  (piestion  arises 
whether  these  schists  may  not  represent  i)eds  that  were  laid 
down  in  the  Trenton  age.  So  far  as  recognized,  the  Trenton 
beds  are  limc.stones  ;  hiit  there  must  have  been  sediments  coeval 
with  those  limestones  in  the  ancient  seas:  still  it  is  but  a  rude 
conjecture  tliat  would  refer  them  to  this  aye.  Thev  are  called 
Loraiue  upon  the  sections.   These  beiis  were  called  ••  Magnesian 

*  Foniicflv  ivj.'iir.U'(l  as  Lower  Helc!erberg,  1ml  ricmly  sliirwti  by  I'rol'.  K.  P.  Whit- 
liulil  lu  bt'Kiiig  to  tlu'  Niiigiiru.— ./»!.  AVv'.  Jour.,  Ill,  vol   xxv,  p.  ;!0S. 


V 


slate"  by  Prof.  Emmons,  and  constituted  the  iipi)er  member  of 
what  he  styled  "  Lower  Tuconic."  The  relations  of  the  lime- 
stones to  the  schists  are  well  showTi  upon  section  IV  in  Mt.  Kolus. 
There  aliout  'jOO  feet  of  the  schists  are  isolated  fr(»m  all  connec- 
tion with  the  main  ran<^e,  and  rest  upon  about  two  thousand  feet 
thicl<nes8  of  limestones,  almost  horizontid  except  at  their  base. 
The  same  schists  reappear  in  what  is  cal.  'd  tlu;  Taconic  range 
of  mountains,  a  few  miles  west  of  Mt.  Kolus.  They  universally 
dip  east,  and  would  l>e  regarded  as  older  than  the  limestones 
except  for  the  section  in  Mt.  Kolus.  This  fact  has  led  to  care- 
ful search  at  the  junction  of  the  two  fornuitions  for  evidence  of 
a  fault.  Se(!tion  V  shows  this  break  very  plainly  in  Tinmouth. 
Section  I  affords  the  most  satisfactory  evidence  of  the  passage 
of  the  limestones  beneath  the  schists  of  the  Taconic  range.  At 
North  Pownal  a  fault  has  broii^iit  up  the  limestones  from  be- 
neath the  heart  of  the  mountain  lango.  To  llie  east,  near  tlie 
Massachusetts  line,  the  limestones  dij)  west  toward  these  schists, 
contrary  to  the  nearly  universal  position  of  these  rocks  west  of 
the  Hoosac  Mountains.  IJy  following  the  Troy  ilt  Boston 
Railn^ad  to  the  north  from  North  Powntd.  we  tind  the  limestouea 
nearly  or  quite  continuous  to  lloosick  Kails,  where  the  charac- 
teristic fossils  of  the  C'liazy  and  calciferous  sandrock  occur  in 
them.  This  section,  therefore,  demonstrates  the  inferior  place 
of  the  limestones  as  compared  witli  the  schists.  This  is  in  the 
heart  of  the  classic  Taconic  grounds,  where  the  late  Professor 
Emmons  deduced  the  conclusions  giving  rise  to  the  existence  of 
the  noted  Taconic  system.  1  cannot  ascertain  tiiat  he  discov- 
ered this  western  dip  in  Pownal,  and  the  consetpieut  connection, 
ledge  by  ledge,  of  his  Stockbridge  limestones  with  the  (,'hazy 
and  calciferous  at  lloosick.  It  is  just  here  that  the  fatal  defect 
to  the  establishment  of  the  Taconic  system,  as  delined  by 
Emmons,  exists.  His  paleontological  arguments  were  better 
than  the  stratigraphical. 


TIIK    CAMBRIAN. 


On  the  west  Hank  of  the  Careen  Mountains,  sometimes  rising 
higher  tlian  the  main  raiigi'.  is  a  band  of  (luart/.ite,  which  re- 
ceived from  Emmons  the  appellation  of  "  Granular  (piartz,"  and 


It  wns  iimdo  tlio  hiise  of  his  Taconic  Hystcm.  Our  Hi'ctions  fthow 
tlmt  it  iiiiint'«li:itfly  iiiidcrlit's  the  calcifcioiis  HiiiKliock.  siihI  liav- 
in^^  foHsilh  Hliniliir  to  IIkjsc  found  clMiswiu'ie  in  llu-  I'otsdam 
BHiidHtoiK',  it  is  clearly  a  mcmbj'r  of  the  Camhrian  Hcrivs.  lii 
80IIU'  (|iiarti'i's  the  ctTort  has  been  made,  iiiisiictH'ssfully,  to  refer 
it  to  the  Middle  Silurian  sandstones.  Upon  sections  III  and 
V'll,  besides  other  localities  nieiitioni'd  in  the  I  HO  I  report,  the 
basal  beds  contain  pebbles  of  blue  (piartz,  which  are  reco<i;ni>!ed 
as  havinj^  been  derived  from  t!ie  adjacent  "gneisses  of  the  (Jreen 
Mountains.  Hence  this  (pnirtzite  has  been  fortned  since  the 
elevation  of  the  Green  Mountains  above  tide  water.  The  cal- 
ciferous  sandrock  had  its  ori}j;in  posteriorly  to  the  (puirt/.ite,  and 
likewise  the  several  other  members  of  the  limestone  }j;roup  in 
their  turn,  and  there  is  a  natural  order  of  succession  in  time  o* 
the  formations  from  the  <2,neiss  to  the  west. 

Three  bands  of  sandstone,  therefore,  are  referred  to  the  Pots- 
dam in  the  Cham|)lain  valley : — first,  the  normal  j^ray  sediment- 
ary beds  at  the  foot  of  the  Adirondacks,  always  known  under 
this  name  since  IHIO  ;  second,  the  quartzite  on  the  flank  of  the 
Green  Mountains  ;  third,  a  ran<;e  of  reil  s mdstone  and  dolomite 
from  the  Canada  line  to  IJridport,  whore  it  is  succeeded  by  out- 
crops of  a  material  not  distinguisliable  from  the  first-named 
band.  Partly  accompaiiyinji;  the  middle  band  is  a  series  of 
slates  and  hard  sandstones,  passing  into  roolinjj;  slates,  called 
"  Georgi.a  (jroup  "  if  the  state  report,  which  carri(>s  such  fossils 
as  Ole.nelliifi  iuuX^bii/elina,  and  is,  therefore,  tlioutjlit  to  be  some- 
what older  than  the  typical  Potsdam  sandstone.  These  are 
partly  connected  with  a  series  of  schists  gradually  increasing  in 
thickness  and  width  of  territory  from  section  VI  I,  east  of  Mid- 
dlebury.  to  the  Canada  line.  The  quartzite  first  named  termi- 
nates lietween  sections  N'll  and  \'III,  save  a«.  it  may  merge 
into  these  scliists.  The  continuation  of  th'^isc  •-■.  iiisi-^  into  Can- 
ada is  an  area  partly  of  Cambrian  and  partly  of  Levis  age. 

We  can  now  understand  the  physical  histor;.'  of  western  Ver- 
mont in  the  early  Paleozoic  age.  The  Adirondacks  and  Green 
Mountains  luid  been  elevated  above  the  sea,  and  constituted  dry 
land,  connecting  on  the  east  witii  tiie  large  Atlantic  area — New- 
fu*;ndland  to  Alabama — and  on  the  north-west  with  the  gen- 
era 11  v  recognized  Laurentian  of  IJritish  America.     The  waves 


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daHliiti};  nt  tho  Vermont  iind  Now  York  shoro  Hmph  ncoutniilated 
the  (|iinrt/  (Ifrivi-d  from  tin    (liHintt'<j;ratioii  of  the  ^jtiu-iKMcs  into 
bunks  of  piirolv  silicioiirt  siindH,  frtMHiciitly  tcinu'd  ••  priiuordiiil 
seu-lx'iK'hi's."    'I'lic  otlicr  umtoriiilN,  of  liner  textiiri',  were  wiiMlied 
out  into  tlie  deeju'r  waters,  but  remlied  Hulllci«'ntl.v  ntur  the  »ur- 
fuce  to  allow  of  the  exiMtence  of  trilobites,  annelids,  and  sea- 
weedw.     Atlenjrth  tlu!  silii-iouH  sediments  ceased  to  aeeunmlute, 
and   'imestones  took    their  place,  fallinj;;  iiown   upon   the  slaty 
foundations.      In   the  Trenton  a<jo,  the  last  of  the  limestones, 
this  sea  became  disconnectetl  with  the  Atlantic  ocean  through 
the  present  Gulf  St.  Lawrence,  as  shown  by  the  distinctively 
American  types  of  life  existinjj  throutihout  the  interior.     'i"he 
limestones  were  finally  eoverecl  by  the  I'lieii  and  Loraine  slates. 
Partial  elevations  of  the  Champlain  country  had  been  in  |»rog- 
ress  during  the  building  up  of  the  C'amltrian  aiul  Cambro-Silu- 
rian,  but  there  must  have  been  a  very  important  one  after  the 
deposition  of  the   Loraine  group.     The  whole  Champlain  valley 
seems  to  have  been  then  raised  above  the  ocean,  since  no  rocks 
of  later  ago  have  been  deposited  in  this  basin  within  the  limits 
of  New  Kngland.     Tho  linal  results  of  all  the  elevatory  move- 
ments have  been  tlu;  crowding  towards  each  other  of  the  prim- 
itive land-areas  ;  the  faulting  of  the  primal  slates  ;  the  raising 
of  the  beach  beneath  Burlington  and  St.  Albans— and  changing 
its  color  from  gray  to  red — overturning  many  of  tho  limestones 
and  sandstones;  developing  the   synunetrical   folds  in  the  red 
sandstone  about  Monkton  and  I-'ertisburg  ;  and  the  alteration  of 
the  calcareous  beds  into  snow-white  marbles. 


THE    CiKKKN    .MOINTAIN    AMULINAI. 


■> 


U 


I 


The  existence  of  the  anti  linal  ridge  of  the  (Iroen  Mountains 
was  the  most  important  oontri' -utiou  to  science  made  by  the  late 
geologictd  survey  of  Vermont,  though  its  value  was  not  then 
ap|)reciated.  Nearly  all  our  sections  illustrate  the  existence  of 
this  structural  feature.  Only  No.  VI  II;  purely  monoclinal  ;  and 
this,  like  VII  and  VIII,  is  to  be  regarded  as  an  inverted  anti- 
clinal. The  elevatory  pressure  seems  to  have  been  greatest 
along  the  middle  part  of  the  state,  so  as  to  have  overturned  this 


10 


main  axis.  In  I  a  mass  of  mica  schist  of  uiuictermined  age, 
possibly  3Ioiitalb!in,  constitutes  the  smnmit  of  the  iiisihest  rid<^e. 
continuous  from  tlie  Iloosac  mountain  over  the  celebrated  tun- 
nel to  No.  11  in  Searsburg.  where  it  rests  upon  the  eastern  Manic 
of  the  elevated  country.  The  gneiss  is  narrowewt  at  the  tunnel, 
and  widest  along  section  I,  where  it  may  readily  be  seen  to  be 
composed  of  three  parallel  axes.  The  more  western  one  may 
not  extend  many  miles  northerly,  and  ic  is  more  like  the  typical 
Laurcntian  than  any  otiier  area.  Very  satisfactory  sections  are 
obtained  in  tl;-3  valleys  of  the  Winooski,  La  Moille.  and  Mis- 
sisco  rivers,  cut  down  across  this  formation  more  than  .'5.000 
feet,  just  north  of  Camel's  Hump,  Mt.  Mauslield,  and  Jay  Peak 
(compare  IX  to  XIII).  Upon  the  high  mountains  the  strata 
are  ap-t  to  l)e  obscured  by  extensive  deposits  of  till.  Logan's 
scheme  of  sti-ucture  involved  the  existence  of  a  synclinal  in- 
stead of  anticlinal,  while  his  description  of  Sutton  mountain* 
showed  that  the  true  structure  could  not  be  suppressed.  Sel- 
wyn,  his  successor  in  oHice,  declares  that  the  physical  character 
of  the  region  entirely  favors  the  anticlinal  structure  for  the 
Green  Mountains  in  Canada.  Prof.  J.  I).  Dana  has  also  an- 
nounced his  conviction  that  these  gneisses  in  southern  Vermont 
are  older  than  the  (juartzite,  and  of  Archa'an  age.t 

In  southern  Vermont,  wiiere  the  elevated  region  is  widest, 
the  rocks  are  usually  well-defined  gneisses,  including  protogene. 
North  of  VI  the  feldspar  diminishes  in  amount,  and  at  length  is 
mauifented  in  scattered  crystals,  seen  chiefly  where  tiie  layers 
are  broken.  An  inexperienced  observer  will  overlook  the  feld- 
spar upon  the  higher  mountains  in  the  northern  part  of  the 
state.  It  is  pro|>erIy  a  feidspatliic  mica  schist.  Adams,  the 
first  state  geologist,  suggest(,'d  the  name  of  •' Green  ^Mountain 
gneiss"  for  the  whole  terraue,  in  view  of  this  marked  litholoo:- 
ical  feature.  We  (ind,  on  examination,  that  this  micaceous 
band  is  proltably  the  e(piivalent  of  a  mica  schist  or  mic;iceous 
gneiss  in  sev(>ral  gneissic  terranes  of  this  age  in  the  Connec- 
ticut iiydrograpiiie  basins  in  both  states,  and  that  it  is  overlaid 
by  hornblende  scliist. 

It  follows,  from   tlie   rehitions  of  th(>  Cambrian  quartzites  to 

*(ir(.lo^'y  (il'Ciuiailil.  ISO.'i,  pujr,.  o,-,i 

t  Quar.  Jour,  ( ;eol.  Soc,  XXXVIII,  397,  1882. 


i 


the  giK'U.s,  tluit  the  latter  is  of  pi-e-Cambrian  age.  The  "  pri- 
mordial sea-beach"  detined  the  western  limits  of  this  ancient 
land.  If  we  nse  a  similar  criterion  for  the  determination  of  the 
eastern  limits  of  this  land,  we  mnst  travel  to  Hraintree  in  Mas- 
sachnsetts,  or  far  down  in  ^^aine,  to  find  thoin.  There  are 
nnfossiliferons  (jnartzites  and  limestones,  probably  the  efpiiva- 
lent  of  these  western  bands,  in  IMymonth,  Vt..  Hhode  Island, 
and  near  the  mouth  of  lVii()bsc()t  bay.  The  tirst  are  about  ten 
miles  in  length.  There  are  also  areas  of  slate  of  undetermined 
awe.  In  later  times  tiie  Conneetieut  vallev  deepened  sufliciently 
to  allow  of  the  <j;rowth  of  Niagara  and  lleldcrl)erg  coral  reefs. 


couur.LATiox  OK  Tin;  (ii!i:i:N   mointain   and  new  uami'shire 

GNEISSKS. 

The  sections  will  enable  us  to  i)r()ceed  a  step  fin'ther.  and  cor- 
relate the  gneisses  just  descril)ed  with  those  of  south-eastern 
Vermont,  the  C'onnecti<'ut  valley,  and  both  llanks  of  the  high- 
lands l)etween  the  Conneetieut  and  Merrimack  rivers  in  New 
Hamiishire.  First  of  nil,  ujjou  Nos.  II,  III.  IW  and  V  the 
Green  Mountain  terrane  repeats  itself  in  the  well-delined  range 
marked  on  the  N'ernionl  map  as  extending  from  Halifax  to  Hart- 
land.  Next,  passing  the  small  (Juilford,  lirattleboro',  and 
Vernon  areas,  we  find  the  terrane  again  rising  with  greater  width 
from  Winchester  to  Fit/.william  in  1.  Swanzey  in  II,  Surry,  (ill- 
sum,  and  Stoddard  in  III.  but  largely  covered  by  later  rocks, 
Acworth  and  Lempstei-  in  l\'.("roydon  and  Springlield  in  V, 
Hanover  and  C'an:ian  in  VI.  Orford  and  Weiitworth  in  VII, 
Haverhill  and  Benton  in  VIll.  IJethlehem  in  IX.  .lefferson  and 
Berlin  in  X.  and  Milan  in  XI.  This  is  the  noitiiern  termination 
of  the  ti'rraui'.  It  next  shows  itself  u|)on  the  Merrimack  sIojjc, 
viz..  at  Peteiborougli  in  II.  Dcering.  Weare,  and  Dunbarton  in 
III,  Warner  in  IN'.  Andovei'  in  N'.  in  very  limited  amount.  It 
seems  on  this  Hank  of  the  highlands  to  lie  more  in  small  patches 
than  as  a  l)road  lielt.  Tiie  next  appenrauci'  of  this  gni'iss  is  in 
the  remarkable  range  from  Mason  (1),  through  3Iilford  and 
Amherst  (II),  IManeheslt'r,  C'andia  in  HI,  Northwood  and  Har- 
rinsiton  in  IN'.  This  range  is  characterizt'd  !)y  the  thoroughly 
crvstalline   saecharoidal    aspect  of  the    constituents.     No   one 


12 


HMHhnr  with  tvpicul  Lnurentim,  ir,.o,Mi(l  will  find  UuusoU  far 
<n>M.  ho,...  hotwe,.,.  M..,s,>nuM<l  DcHMliel.l.  Mo,i„  IJ.Hin  and 
m.u   ...t    L.   no,ll...a.st.n.  oxt..,„i,,  of  th.   p,.,.vi,...slv   .n.  - 

tlOIU'd   (riiCISSIC    W.iVC. 

.     •l""'  ^■•  \l.  n.Kl  VII  is  .....odi.M-  .•on,s,mMu...s  miv...  ..Mrllv  oo- 

nu-Hl....,,  w,.l.    „,„  l.v.,n.,n„,i.i,.  l.si..  ,.f  L,,.,  Wi.,.,!pis.o.oe 

Ins  .n.,,  ,s  ,.oio,-c.,l  ,.,.o,.  ll..  u,a,..  suj^^.^ts  a  ..o.lh-we.t  ,ir 

..•n.  a  ,..„,„..,,,  uvn.l.     Co.u,.as.s  „l.s..-vations,  l.ow.v.r,  show 

"  "".'\''-"i''^'  ♦"  '"'  t'-  -■""'-  ''i--tion  ;   h..K...,  th.  whole  of 

tlu-  or,.,,..l  an.:,  is   ,.ot  visihl..  hoi..^,  conc-ealed  hv  h,to,-  for.na- 

'>"s.      'l"s.sti„.ln-oad.stofalIof,!„te.Ta,u..s;and   it  comes 

U.      h.    ^„.„„„s.o.ee  laia.  expo.u.vs  fo.-  g,-a,.ite,  ■...t  the 

..s  o.  ,oi,a  ,o„  ,.a„  al,..ost  always  he  disce,.,..d.     The  dillicultv 

><  d,s  ,„„„sh,.,o.  the  two  ,.oeks  is  ...Ue,.  i,.  the  Mai,.e  tha,.  tl/e 

'="^''  ";':'•""-     /  !'<•  dese,-i,,tio„s  i^iven  by  Selwy.,  to  the  oldest 

La.ne,,  ,a,.  ^„e.ses  of  Canada  will   apply  well  to  those  in  the 

•"-  'i->.u-..      1  he  next  fol,,  is  seen  at    Nashua  an<l  Hudson  in 

_H-npstead,nII,a,uMVest    Kppi,,.  i,.   ,„.     There  a.-e  still 

.-■•;--<>'  sn.all  si.e  below  scn-tion  III.  espeeiallv  in  Massa- 

cl.use Us    wl,e,.e  o,.,-  pnMished   n,ap  shows  the  no,-th-east  ternd- 

m.s  ot  (he  band  wl,i..h  ha.  affonled  (he  Enzoo.  in  Ch^hnsfo,.! 

Inns.nueh  as  (h.se  seve,.al  ^neissi.  ,,,n^es  rese.nbie  one  an- 
'»<''^'.''-  =>"'l  '-Nln''it  the  usual  pheuo,,,.,.,  „f  st,atiu,aphieal  eon- 
;"'^'';:'"-  -''*""-•  '-  '•••I'lin^'  lu.ueath  supe.-io,.  'fo.Muations  or 
•-<i"-|.  ove,-  s„!|  u,o,va„eieu,  .roups,  it  is  but  a  neeessarv 
av„e,.ah.a„ou.o,.o,K.l,H,e,ha(.heyeau,e  inb.  existence  in  the 
sMuu.  ^eolo^ieal  a^e.  a,ul  1  hat  ( hey  a,v  all  (o  b.  ranked  as  the 
7'"^-'-'>s  of  (he  Cveu  Mo„u,ain  sc-ies.  p,e-Cambnau.  -Vr- 
H.a.u,.o,|.:o/oie.  li  ma  v  be  ,vn,a,ked  (hat  th.  ,i,st  ha>  a  north- 
^^••'>-   "vnd   ,„   sou(lu,M   \enuo,„.ve,.oin,o.   „,„,,   .,,,t,,,,v   j,,   ,,,, 

7;l'''-  I'-'t  <>'•  'he  s,a,...  :,,ul  ,,ot  ex(e,,di,,o.  in,o  the  do,.,iuion 
"'■■'"••"'••'  '"•*••'■  "'"'  •^^'•'".v  u,ile..  Th.  othe,-  .•anues  ,r,,u. 
-i.ilveou,seu,o,veaste,ly.  and  lie  uea,iy  in  tl,e  „on„al  .uu-th- 
i-'M  ninov  o(  (heroiavspondino  (eiTaue>  south  of  N.w  Ku.dand 
-  n,  the  hi,l,la,.d>  of  N..W  Vo,.k.  New  .le-^sey.  and  (h;  Blue 
•^•d^v  ol  \  „.on„a.  U  ..  have.  the,vfo,-e.  an  extensive  -n'oup  of 
gueissu.  a,vas  esseutiallv  .o,ui,)nous  tYuu,  Newfoundland  to  Vla- 
'^^""^'   *'"   the  Atlanti.   iuude,-   of  this   e.-ntineut.     Tuev  a,v  of 


f 

1 


f. 

I 


4 


18 


ir 
1(1 
1- 


Eozoic  :i2;o,  coeval  with  the  formations  of  the  Laurontiiui  liish- 
lands,  and  developed  along  a  different  line  of  growth.  They 
constituted  an  Arohieaii  Atlantis,  now  parti;  lly  submerged,  hut 
playing  an  important  part  in  the  building  up  of  the  North  Amer- 
ican continent. 


THE    OLDKST   OK    TIIIC    (JNEISSES. 

These  common  gneisses  overlie  a  peculiar  rock,  whose  largest 
development  follows  the  water-shed  between  the  Connecticut 
and  jMerrimack  svstems  of  drainage,  the  tract  of  iii<;hest  eleva- 
tion  in  the  state  south  of  tlie  White  Mountains,  and  tlic  group 
passes  beneath  the  mountains  north  of  the  Merrimack  basin. 
This  rock  is  a  gneiss,  containing  distinct  crystals  of  orthoclase, 
from  one  lialf  to  three  inches  in  length,  which  are  usually 
arranged  in  lines  of  sup])osed  ])edding.  A  more  conspicuous 
ledge  is  rarely  seen  ;  and  hence  geologists  have  universally  rec- 
ognized and  described  the  rock.  It  is  the  AiKjtnt  ijiieiss  of 
Europe,  and  Logan  mentions  it  as  a  constituent  of  the  Lauren- 
tian  in  Canada.     It  is  not  met  with  in  Vermont. 

Nearly  tiiirty  areas  of  this  formation  have  been  delineated  on 
the  New  Hampshire  map.  The  largest  extends  continuously 
from  J.ii'frey  to  Groton,  dips  beneath  mica  scliists  to  rise  again 
in  Ellsworth,  continues  to  Franconia,  and  then  underlies  the 
Bethlehem  grouj)  of  gneiss  to  arise  for  the  last  time  to  the  sur- 
face at  the  Wing  Road  railroad  junction.  The  extreme  points 
thus  indicated  are  10')  miles  apart.  On  section  I  this  rock  just 
rises  to  the  surface  in  Kindge  ;  on  J  I.  tlu;  southern  extremity  of 
the  main  range  is  touclied  in  .laftrey  ;  on  III.  IV,  \',  ^'I,  and 
VII,  the  rock  is  very  conspicuous.  Two  ranges  are  seen  in  VI, 
VII,  and  \TI1,  and  it  uncomformably  underlies  the  other  gneiss- 
es in  several  instances.  The  api)arent  doubling  in  \l  is  occa- 
sioned Iiy  the  crossing  of  a  crooked  range.  Other  rocks  inter- 
stratified  witii  and  integral  parts  of  the  formation  are  ordinary 
gneisses,  hard  mica  scliists,  ferruginous  (pmrtzites.  and  librolite 
aggregates.  The  stratification  is  often  obscure,  and  entirely 
obliterated  in  many  localities,  or  where  the  crystals  of  feldspar 
are  irregularly  disposed.  No  tower  group  than  this  has  been 
recognized  in  any  sections,  or  anywhere  else  in  New  England. 


14 


1 


IIOKNBLENDE    SCHIST    (JKOUI'. 

Ha  vino:    asrortainod    the    stnitigraphical     rel.itions    of    the 
gneisses,  we  find  the  first  rock  coverin-,.  ihem  to  he  a  band  of 
hornblende  schist,  occasionally  feldspathie,  and  not  unfrequently 
1,500  feet  thick.     It  is  best  understood  in  the  southern  parts  of 
our  held,  partly  because  better  exposed,  and  partly  because  it 
has  been  less  studied  in  the  north.     First  noticed  in  the  Guil- 
ford  and  Hrattleb(,ro',  Vt.,  anticlinals  I  and  11,  it  was  detected 
only  by  exploration  to  hold  the  same  position  on  boti,  flanks  of 
the  Hahfax-IIartland  gneiss  II.  III.  and  IV.     On  I  it  also  over- 
lies the  Green  Mountain  terrane.     In  New  Hampshire  it  borders 
a  tract  of  gneiss  between  II  and  III  in  Cheshire  county  ;  flanks 
the  west  border  of  the  Hanover  gneiss,  and  covers  tl/e  Canaan 
synclinal  in  VI;  and  overlies  gneiss  in  Surry,  III,  and  Haver- 
hill, VIII.     There  is  a  continuous  range  of  it  close  to  the  Con- 
necticut river,  between  Cornish  and  Haverhill.     In  fact   it  is  so 
constant  next  the  older  gneisses,  that  if  it  be  clearly  absent,  the 
presence  of  a  fault  or  of  an  unconformity  may  be  assumed.     In 
Vernon  it  encircles  an  nrea  of  gneiss,  and  the  structure  indicated 
IS  that  of  an  overturned  anticlinal.     The  rocks  over  the  horn- 
blende are  the  green  schists  formerly  called  talcose.     This  is 
proved   upon  I,  III,  IV  in  Vermont  and  the  Connecticut  river 
range  about  Cornish.     Similar    beds    are    associated   with    the 
green  schists  in  Marlborough,  II,  and  the  Ammonoosuc  gold- 
field.     It  seems  more  intimately  connected  with  the  green  sdiists 
than  with  the  gneiss,  though  often  only  the  hornblende  band 
will  be  present. 

HURONIAN. 

This  name  is  used  as  a  matter  of  convenience  to  desi<>-nate  all 
the  various  schists  of  chloritic  and  argillitic  aspect  o'verlvin^ 
the  gneisses  and  inferior  to  the  Cambrian,  so  far  as  known" 
The  tcrraiies  in  Vermont  and  western  New  Hampshire  are  the 
ones  that  have  been  st.iciied  the  v,,ost,  and  are  the  most  valua- 
ble for  the  determination  of  age,  l)ecause  more  nearly  related  to 
the  original  Canadian  exposures  called  by  this  name.  '  The  supe- 
riority of  the  main  Huronian  belt  upon  the  east  side  of  the 
Green  Mountains  to  the  gneiss  is  obvious  upon  every  section 


1 


16 


from  I  to  VIII.     This  view  is  confirmefl  upon  II  to  V  by  the 
inferior  position  of  the  Halifax-IIarthind  range  of  gneiss. 

The  Connecticut   river  range  is  first  seen   in  IV,  and  from 
thence  lo  Maine  and  Canada  upon  every  section  it  adjoins  the 
hornblende  schist  or  older  gneisses,  resting  upon  them.     From 
VI  to  XI  it  is  easy  to  connect  the  Green  Mountain  and  Connec- 
ticut river  ranges  by  a  synclinal  fold.     V\)ou  XII  and  XIII  the 
direct  connection  is   interru[)ted   by  granites  and   schists  that 
seem  to  occupy  the  i)lace  of  the  lialifax-Hartland  range,  II  to  V. 
The  apparently  overlying  position  of  the  Iluronian  west  of  the 
calciferous  in  IX  and  XIII  is  due  to  inversion,  as  proved  by  the 
occurrence  of  the  fossiliferous  Helderberg  in  similar  position 
just  to  the  north  of  XIII  in  Canada  (Lake  Memphremagog). 
West  of  the  Green   Mountains   the   Huronian  has   its  normal 
development  in  Canada  and  in  the   northernmost  counties   of 
Vermont,  gradually  diminishing  in  breadth  southerly.     It  is  not 
found  south  of  VII.     In  southern  New  Hampshire  the  argillitiCr 
quartzose,  and  micaceous   divisions  predominate  nearly  to  the 
exclusion  of  the  chloritic  schists,  which,  with  the  characteristic 
dolomite,  is  seen  in  Raymond  and  Derry.     Steatite  occurs  in  it 
at  Francestown  in  the  ferruginous  slates,  and  in  the  mica  schists 
of   Derry.     All  the    schists  referred   to  this   series  invariably 
overlie  the  gneisses. 

MONTALBAN. 

So  far  the  assignment  of  the  formations  to  their  proper  order 
has  been  comparatively  easy  ;  but  the  introduction  of  the  word 
Montalhcm  immediately  suggests  discussion.  Inasmuch  as  the 
typical  locality,  as  shown  by  the  name,  lies  within  our  territory, 
tiie  relations  of  the  group  must  be  brielly  discussed.  The  name 
of  '"White  Mountain  Series"  was  tirst  employed  by  myself  in 
IrtO'J.  as  a  matter  of  convenience,  in  the  discrimination  of  the 
crystalline  rocks  of  the  White  Mountain  region  and  their  exten- 
sion into  Massachusetts.  Previously  our  geologists  had  usually 
reo-arded  these  ervstalline  schists  as  of  Paleozoic  age,  prol)ably 

*  '111 

Devonian.  My  studies  in  the  Ammonoosuc  district  enal)lecl  me 
to  advocate  their  pre-Silurian  origin,  and  hence  to  give  them  a 
special  ntune.  It  was  not  intended  to  describe  them  as  a  .s»/.s?em 
separate  from  the   Laurentiau.  though  the  conviction  had  been 


If) 


more  tlian  once  stated  in  puhlic  tliat  tli 
prove  to  belong  to  a  mot 


applied  with  tlii 


•e  recent  series.     Tlii 


ese  rocks  would  probabl 


IV       ♦ 


s  name  was  also 


what  si„,N„,.  .,,,0.  .,f  .0  't  „    ■i,,,",r,;',';''''«'  ">";- 

ciferous  mica   schists   in    our   reno.t^       r,.  «"  'P  and  cal- 

-■■...10.,  „„.,..  t„i.,  ,„»ig,„ui„„  'r:„f  ;;Zt  tr' ;;  "^ 

a  »y.st„„,  below,  „„„  tl,e  „H,o,.  „l.„ve,  the  H  ,™  i  ,  °  .T  ""' 
yet  given  i,s  aiiv  nioofs  of  fl„.  u,l  """."■"'■  "«  has  uot 
.■ived  from  the  .t,  dv  of  th  .  "  "«^"  "'  "'"  M"""'"..".  de- 

elusions  have  he       1  Ull        *'"""""" '"."."it',  hut  the  con- 

mica  »ehi»t  g,.o  „  la   .  t,',  ,  •  •■"■'"  '■"""'™'-     •"'"-  i»  " 

that  the  feldspathie  r.^:!::^  ^^JZ  ^^^ ^  'T'' 
belong.  tOH„  oldc,.  .e,.ies,  whiehtni^lit  t  «„  ,"'  it;'"""" 
has  named  it  in  North  C-i.-oh-nn    h.  V  ^-  ^^^'''^' 

examined  the  .nVel  of  Ta      AV     '  ''•'"'  '^""•^"^•''^"-     ^  "^^ve 

i^.-  Hunt,  who;i:.::iit^2:;z:r:;:,  -rr-^  ---^ 

has  been  shown  above  to  be  Cea         1  e,  tt  n  the  if  ^""'" 
and  as  it  constitutes  the  axis  of  th;  P  Vr  ^^•"■0'"'^». 

by  him  to  be  thus   a  In^    •  ,        '"  ^^lountains,  allowed 

series,  as  defuHHl  bv  hZ        ,  "      '"""  ''''  ''''  ^^^'^"^''^"'- 
.!»  utiiiKd  i,\  Hunt,  embraces  two  oroiijis  of  ,„-,.  i» 

ent  age.     Hence  the  woid  1ms  heen  nsed  1,^,^  "'■',""*"- 

"'7'i..l.l.v  ernpio,  it  in  its  original    ig      .    ti      o  rr.i     '"  "" 

New  Ha,,.,.:',;;!";:  o "  'xii.  ':,::'„:';';:;f-"-'-  -'  '"■"'  ^"  ''.^ 

position.     Theexalnples  cited    ,i'l;"'.;,:7=  ";'"  J""^'- 
eii.  part  of  the  st,.te.  'Mwil  ...e  hom  the  north- 

-MIC.V   SCHISTS, 

thus  t.„   described,  especially   i„  southern  New 

*Vol.  II,p.  (ioG, 


17 


V   f 


I 


Hampshire,  is  miqnestionable.  No  autlinr  who  has  devoted  any 
attention  to  tiiese  groups  lias  snp;<xested  an  inferior  position  for 
them.  They  may  he  called  Silurian.  C'auihrian,  or  pre-Cam- 
brian,  according  as  each  author  is  inclined  to  regard  New  Eng- 
land very  ancient,  or  on  the  verge  of  the  Paleo>5t)ic.  Such  of 
the  Rockingiuvm  grou|)  as  is  not  referred  to  the  Huronian  be- 
longs here,  as  shown  in  the  Pack  Monadnock  Mountains  (II), 
Belmont,  Gilmanton,  and  Milton  (\').  It  constitutes  the  sub- 
stance of  several  interesting  nioinitains.  like  the  Pack  Monad- 
nock,  'rem[)le,  and  Lyndeborongh.  west  of  the  [Merrimack,  and 
Catamount.  Fort,  Xottingham,  lUiie  Hills.  lUue  Job,  Ilussey, 
Chesly,  and  Teneriffe,  to  the  east.  This  orographic  feature  is 
paralleled  in  Mts.  Monadnock,  Kearsarge,  and  Raggetl,  of  a 
possible  older  group  carrying  andalusite. 

In  the  Connecticut  valley  there  are  10,000  or  12,000  feet  of 
mica  schists  and  associated  rocks.  Many  of  them  are  charac- 
terized by  the  presence  of  staurolite  and  garnet,  and  by  this  fea- 
ture are  distinguished  from  a  contiguous  band  of  Cambrian  clay 
slate.  Its  basal  member  is  a  quartzite.  1.000  feet  thick  in 
Cheshire  and  Grafton  counties,  and  frecjuently  occurring  in  im- 
mense masses,  as  in  Croydon,  Grantliam,  Moose,  Cuba,  and 
Piermont  mountains.  This  rock  resembles  the  Potsdam  at  the 
west  base  of  the  Green  Mountains.  In  Washington  county, 
Vermont,  it  may  be  replaced  by  a  quartz  schist,  often  micaceous. 
The  calcareous  member  occupies  a  great  many  square  miles  in 
Vermont,  amounting  to  more  than  one  fourth  of  the  entire  area 
of  that  state.  Logan  regards  the  Canadian  extension  of  this 
band  as  of  Niagara,  or  upper  Silurian,  age.  Dana  supposes  the 
fossils  at  Hernardston,  Mass.,  to  be  so  connected  with  this  ter- 
rane  that  they  determine  its  age — being  upper  Silurian  or  De- 
vonian. There  are  many  ditlicnlties  involved  in  readily  refer- 
ring this  entire  series  to  the  upper  Silurian  ;  but  if  any  collector 
will  Ijring  in  fossils  from  characteristic  localities  proving  its  Ni- 
agara age,  there  will  be  uoJiing  in  our  interpretation  of  its  strat- 
igraphy inconsistent  with  such  a  discovery.  The  rocks  are  evi- 
dently the  newest  of  any  of  the  great  systems  of  strata  described 
in  our  reports.  To  elevate  them  to  the  upper  Silurian  would 
not  carry  any  higher  the  chloritic,  silicious,  or  feldsi)athic  schists 
already  enumerated. 


IS 


A  brief  disfii»si(m  of  llu-  stratiiirapliy  of  the  Coos  and  ealcif- 
eroiis  mica   schist   croups   will  show   wiiy  they  take   their  hifih 
place  ill  .)iir  NVsteni,  and  illustrate  the  nature  of  the  dillietilties 
encountered  in  undersfaiidino-  the  various  dips  and  overturns  of 
the  strata  in  our  Held.     These  groups   are  not  separated  in  our 
sections,  as  they  are  supposed  to  he  essentially  the  same  series, 
and  their  litholoiiical  differences  sueh  as  result  from  loeal  (-auses. 
The  ealeareous  division  lies  chietly  in  Vermont,  and  on  XI.  XII, 
XIII,  west  of  a  orniiitic   area.     The  most  eastern  of  the  mic.a- 
ceouJ  iireas  upon  XIII.  and  a  part  of  the  same  in  V.  are  ealca- 
reous  ;  all  the  other  schists  of  this  ajiv  in  New  Ilami)shire  lack 
tlie  limestone.     There  is  no  foundation  for  the  statement  some- 
times  made,   that  the   staurolite  and  andalusite   crystals  have 
been   produced  l.y  the   proximity  of   oranite   or  other   iirneous 
rocks  when  erupted.     On  the  contrary,  these  ii-neous  rocks  are 
common  in  the   calcareous  areas  where  silicates  art'   rare,  and 
are  absent  where  these  cruciform  minerals  are  abundant. 
"^  The   natural  relations  of  the  micaceous  group  and  the  neigh- 
boring series  are   displayed  upon  VI,  VII.  VIII.     Four  series 
of  rodvs  are  disposed  in  a  synclinal  form  :  the  micaceous  group 
is   at  the  summit,  underlaid  fust  by  clay  slate,  second  by  the 
Huronian,  and  third  by  gneiss.     The  synclinal  is  complex,  as  is 
to  be   expected   where  elevating   forces    have   l)een   so  active. 
Upon  VI  there  are  nine,  and  upon  \'II  there  are  seven,  axes  in 
the  mica  schist  west  of  the  Connecticut.      So  many  groups  in 
synclinal  attitude  must  represent  the   natural  order,  and  hence 
afford  a  basis  for  exi)laiiiing  apparent  exceptions  by  overturns, 
faults,  and  unconformities.     Upon  the  other  sections  some  one 
cr  more  of  these  four  groups  are  wanting,  but  those  present  in- 
variably sustain  the  same  relations  to  one  another. 

The  calcareous  divisicn  is  widest  where  the  natural  relations 
of  the  four  groups  are  manifested.  To  the  south  of  VI  it  has 
narrowed  very  nuich,  and  lies  further  east  than  the  axis  of  the 
area  northwards.  This  deHection  has  been  oc-asioned  by  the 
elevation  of  the  Ilalifax-Hartlaud  range  of  gneiss,  since  it  occu- 
pies the  line  of  the  central  axis,  and  has  its  northern  end  en- 
vironed by  the  mica  schists,  as  shown  on  V.  Repetitious  of 
this  gneiss,  with  the  accompanying  hornblende  schist,  are  seeu 
upon^I  and  II,  and  there  are  others  in  Massachusetts.     It  would 


y 


Ill 


seem  !vs  if  tlic  clay  slato  and  i\w  Iluroiiian  were  less  constant 
than  the  mica  schists  and  y;neiss,  since  Ihcy  do  not  afjpear  along 
this  range.  The  eastern  bund  of  the  llnronian  does  not  appear 
at  all  south  of  III,  and  its  place  ovit  the  gneiss  may  he  takeu 
by  the  hornblendic  group.  The  absence  of  the  "'ay  slate  alone 
is  sutlicient  to  enalde  us  to  assume  the  existence  of  an  uncon- 
formity of  the  mica  schist  over  the  hornblende  group.  If  tlie 
slates  and  Iluronian  were  ever  deposited  over  the  Ilalifax-Ilart- 
land  gneiss,  they  have  been  sul)se(iuently  removed  by  elevatiou 
and  denudation  before  the  deposition  of  the  mica  schists. 

An  exiimiiiatiou  of  the  more  nortiieru  sections  shows  that 
older  or  eruptive  rocks  take  tiie  placi'  of  the  Ilalifax-Ilartland 
gneiss  of  IX,  XII.  and  XIII.  Upon  IX  tlie  granite  has  uplifted 
the  adjoining  strata,  so  that  if  our  order  of  the  groups  were 
determined  by  their  succession  on  this  lint',  we  would  call  the 
micaceous  rocks  older  than  the  slates,  and  the  Iluronian  newer 
than  the  slates.  The  intrusion  of  this  immense  mass  of  gi-anite 
gave  an  unusual  dip  to  the  mica  schists,  and  being  of  unyielding 
composition,  the  more  tiexiltle  slates  and  chhn'itic  schists  were 
overturned  upon  both  sides.  The  fundamental  gneisses  upon 
bot'.i  sides  seem  to  have  been  unaffected,  except  that  they  stand 
more  nearly  erect  than  before.  Ui)on  XII  and  XIII,  the  gran- 
ite is  larger  in  amount,  and  accompanied  by  gneiss  and  Huro- 
nian, — though  scarcely  shown  ni)on  the  profiles, — and  the  over- 
turns are  less  conspicuous.  Just  to  the  north  of  XIII  the  over- 
turning of  the  Huronian  is  made  more  obvious  by  the  presence  | 
of  Ilelderberg  fossils  in  strata  dipping  beneath  it  The  eruptive  ] 
granites  have  [lenetrated  fissures  in  the  mica  schists,  so  that  | 
the  latter  nnist  be  the  oldest.  Logan  and  the  Vermont  report 
regarded  the  granites  as  of  Devonian  age,  because  the  disturbed 
rocks  were  thought  to  be  upper  Silurian. 

It  seems  likely  that  these  granites  npon  IX,  XII.  XTII,  were 
connected  with  the  uprising  of  the  Halifax-IIartland  gneiss  in 
southern  Vermont.  If  granite  is  derived  from  the  fusion  of 
schists,  these  bosses  might  have  originated  from  the  melting  of 
rocks  connected  with  that  range  deep  down  in  the  earth.  Small 
areas  of  gneiss  are  connected  with  these  granites  u|)on  the  same 
axial  line  in  the  middle  of  the  calciferous  groups,  and  Selwyn 
finds  them  near  the  United  States  border  in  Canada,   saving 


r 


1 ' 


20 


these  "  aro  appuictitly  repetitions  of  the  crystalline  schists  of 
the  unKM  Sutton  mountiiin  iintidinal  to  the  north-west."*    C;ran- 
ite-also  occurs  there.     Tiio  end  of  the  .^niciss  ranj^e  is  connected 
with  the  granites  upon  IX,  XII,  and  X  111  by  an  anticlinal  line, 
seen  upon  every  inlrrniediate  section.     I'pon  VIII,  X,  and  XI 
this  line  is  developed   into  a  mountainous  range,  and  the  strata 
have  very  low  dips.     Thus  the  normal  structure  of  this  great 
basin  is  that  of  a  synclinal,  with  an  anticlinal  in  the  middh-  more 
highly  elevated  than  the  sides,  and  sometimes  bringuig  up  the 
uiuleilying  gneiss.     This  feature  is  not  conlined  to  the  calcifer- 
ous  gri)UiK  "  Dozens   of  similar  folds  can  readily  be  seen  upon 
our  chart;  and  the  discovery  of  this  type  of  structure  aids  nia- 
teriallv  in  the  understanding  of  the  New  England  folds.     Au- 
thors "have  pointed  out  a  similar  type  of  basin  in  the  Apptda- 
chian  regie, n  of  Pennsylvania  and  Virginia,  as  instanced  in  Tay- 
lor's sec^tiou  across  the  coal  measures  near  Nesquehoning,  Penn. 
'Jliere  is  great  significance  to  be  attached  to  the  subordinate 
foldings  of  the  calciferous  group  apart  from  this  central  line, 
lu  the"  middle  of  the  area  upon  I,  the  underlying  hornblende 
rock  is  brought  up  twice,  and  tiiere  are  as  many  as  live  folds. 
Upon  III  the"strata  are  entirely  monoclinal,  and  separated  by  a 
band  of  clav  slate  and  a  fault  from  the  non-calcareous  division. 
Along  White  River,  upon  VII,  but  not  delineated  in  our  figure, 
we  have  discovered  a  horizontal  fault  in  this  group,  and  there 
must  have  been  an  extensive  shoving  westward  of  part  of  the 
series.     The  effects  of  the  dislocation  have  not  been  observed 
outside  of  the  formation,  nor  for  a  distance  of  more  than  r,00 
feet. 

THE   OUKUX   or    GUANrrK. 

One  of  the  subjects  elucidated  l)y  the  study  of  the  New  Hamp- 
shire rocks  is  the  origin  of  granite.  Owing  to  false  theories, 
our  predecessors  have  supposed  it  to  have  been  derived  from 
the  semi-fusion  of  stratified  rocks.  Careful  studies  in  the  field, 
and  the  new  methods  of  investigation  with  the  microscope,  are 
leading  in  the  direction  of  purely  igneous  eruption.  Two  ex- 
cellent" illustrations  are  at  hand,  the  one  from  Mt.  Willard,  and 
the  other  from  :Mt.  Ascutney. 

♦  Geoloyy  of  Cumida ;  n  port  of  progri!:?s  for  I87'.t-Sn,  piige  5. 


21 


MT.     WIl.l.Altl). 


'I'liis  iiioiintuin  in  uciiily  ."5. ()(»(»  feet  al)()ve  the  sen.  and  nearly 
1,000  feet  above  the  Notch  at  the  Crawford  Mouse.  Most  of  it 
is  composed  of  a  hard  mica  schist  or  jj;neiss  ltelon<>;inij;  to  the 
Montali>an  series,  and  is  the  end  of  this  rock  as  developed  in 
the  Presidential  ran<j;e.  Tho  mountains  to  the  west  of  the  Saco 
rivor  consist  of  eruptive  liianites,  whicli  have  Iteen  extruded  and 
l)oured  over  tliis  i\Ioii(all»an  i^roup.  Two  separate  eruptions 
are  noted  at  jNIt.  Willard.  The  first  and  oldest  is  tcrnjod  Conway 
granite,  or  a  coarse-<;rained  rock  with  l)iotite  foi'  its  mica.  It 
once  lilled  tiie  whole  valley  of  the  .Saco  in  the  White  .Mountain 
rei^ion.  and  continues  north-westei'ly  throu<i,ii  Mt.  Willard  and 
the  Mts.  Tom  and  l{osel)i'ook  ran<j;es.  The  other  is  tei-med  Al- 
bany granite,  both  these  geo<>i'apliical  names  being  derived  from 
the  adjacent  towns,  where  they  are  admirably  develojied.  This 
Albany  granite  seems  to  have  l)een  a  i)urelv  iiineons  mass,  com- 

».      t5  1.1- 

ing  u|)  between  the  Conway  on  one  side  and  a  compact  andalii- 
site  mica  schist  upon  the  other,  termed  the  Ivearstirge  group, 
from  its  occurrence  upon  ^It.  Kearsaige.  The  mica  schist  haa 
been  alYected  by  the  contact  of  a  melted  ni.'iss  in  such  a  way  as 
to  clearly  prove  that  the  Albany  gi'anite  was  eruptive.  The 
peculiar  effects  of  this  intrusion  are  called"  contact  phenomena," 
and  they  have  been  produced  only  by  the  presence  of  a  hot  liq- 
uid adjacent  to  an  earthy  rock  capable  of  alteration. 

The  Montalban  njcks  were  terribly  shattered  before  the  pro- 
trusion ("  the  Conway  rock,  and  tiie  fragments  cemented  by  a 
fine-grai  d  granite,  which  never  passes  into  the  former.  The 
breccia  thus  formed  is  finely  shown  at  the  railroad  house,  a 
mile  south  from  tiie  Crawford  House.  A  few  hundred  feet 
farther  south,  the  Conway  granite  is  well  shown,  luit  the  con- 
tact l)otween  this  and  the  Albany  cannot  be  seen  along  the  rail- 
road, rt  is  necessary  to  climb  the  stoei)  south  side  of  Mt.  Wil- 
lard to  find  the  various  series  of  rock  altered  by  contact.  The 
Conway  granite,  having  once  passed  through  the  fire,  is  not  al- 
tered, and  therefore  tln>  changes  to  be  described  are  altogether 
in  the  schists. 

The  AUiany  granite  is  char.acterizi'd  1)y  tiie  presence  of  crys- 
tals of  feldspar  so  numerously  scattered  through  the  mass  as  to 


I 


22 


!  ',1 


give  it  u  (Spotted  apiK'iirunce,  while  llu;  matrix  is  a  jjivy,  lliic- 
graimliir  aji<rr('<;ato  of  iiraiiitit!  minerals,  somowluit  io«i'ml'!iiig 
the  mixture  (tf  peitper  ami  salt.  In  om  early  reports  this  gran- 
ite had  Iteen  called  "  spotted,"  and  also  ''  trachytic,"  on  aeoount 
of  these  features. 

Wlieii  t'xamined  mieroscopieally,  the  line-grained  mass  shows 
qnartz  in   formless  grains,  with   tliiidal  inelusions.   hornhlende, 
liiotite,  magnetite,  and  apatite.     Angito  and  rtnor-spar  are  also 
freqnent  constitnents.      Hut  the  marked  individuality  is  given 
by  the  uniform  presenee  of  well-crystalli/ed.  scpiaro  prisms  of  zir- 
con.     Kvery  sample  of  this  rock  from  Mt.  Willey.  examined  hy 
Dr.  Ilawes.  showed  an  abundance  of  zircons,  which  arc  white, 
clear,  glassy,  and  sonietimos  yellowish.     The  large  orthoclase 
feldspar  crystals  are  known  to  mineralogists  as  Carlsbad  twins. 
This  descrii)tion  represents  the  normal  character  of  the  gran- 
ite ;  but  both  to  the  right  and  the  left  of  the  centre  prominent 
differences  manifest  themselves,   which   are  thus  described  by 
Dr.  Ilawes:  '^Vt  a  distance  of  one  hundred  feet  from  the  con- 
tact, the  crystals  that  form  the  granite  have  become  smaller,  with 
the  exception  of  the  large  feldspar  crystals,  which  are  in  conse- 
quence  more  conspicuous.     At  a  distance  of  sixty  feet  a  ten- 
dency in  the  (piartz  to  assume  crystalline  forms  is  noticed,  and 
the  rock  Itegins  to  appear  porphyritic.     At  fifteen  feet  from  the 
contact  with  the  schists,   the   quartz   is   found    in  well  delined 
dihexagonal    pyramids    as    large   as   peas,   and   these  with  the 
Carlsbad  twins  of  orthoclase  are  imbedded  in  a  ground  mass  no 
lon<rer  resolvable   bv  the  unaided  eve  or  lens.      I'ijou  the  con- 
tact  the  ground  moss  is  nearly  black  in  color.  Hinty  in  texture, 
and  apparently  homogeneous.     The  Albany  granite  has  become 
a  ([uartz  porphyry. 

''The  accomi)anying  microscopic  changes  are  as  striking. 
Api)roaching  the  contact  there  is  a  continual  diminution  in  the 
amount  of  the  hornblende  and  the  size  of  its  crystals.  There  is 
a  corresponding  increase  in  the  amount  of  the  biotite,  which 
finallv  entirely  rei)laces  the  hornblende.  These  biotite  crys- 
tals are  at  lirst  (juite  large,  l»ut  they  diminish  rapidly  in  size 
near  the  contact,  and  u[Hjn  the  contact  are  reduced  to  a  dust. 
The  ground  mass  which  makes  its  appearance  between  the 
quartz  and  orthoclase  crystals  grows  firm,  but  upon  the  contact, 


thouiili  of  extiviiu'  flin-ness,  it  is  .still  entirely  cryHtiillinc.  In 
tliiH  mouiKl  iiiii»!s  iill  tilt!  minerals  «)f  the  <iiiinite  fcnind  in  speci- 
raens  (liwtsint  from  the  eontaet  are  re(.;oji;iii/al»le,  l»nt  near  the 
contact  no  imlivi.liml  erystals  ean  be  determined.  In  this 
sorieH  of  ehan<;eH  all  the  minerals  have  taken  part  except  tho 
twin  feldspars  and  the  zircons. 

"These  moiliiications,  \vhi(,'li  are  repeated  in  a  less  conspic- 
nons  manner  npon  approachin<j;  the  contact  witii  the  granite 
npontlie  opposite  side  of  the  nniss.  are  sncli  as  mi<j;ht  l»e  induced 
in  a  molten  eruptive  mass,  which  like  modern  lavas  contained 
some  crystals  already  found  at  the  time  of  eruption  by  the  etTect 
of  contact  with  cold  walls,  the  hydrous  nature  of  one  and  the 
anhydrous  nature  of  the  other  being  factins  modifying  the 
extent  of  the  effect." 

The  sciiists  of  the  Kearsargc  group  consist  of  (piartz,  mnseo- 
vite  and  chlorite,  with  many  layers  tilled  with  l)eantifnl  pencils 
of  andalusite.  Unimportant  accessories  are  biotite,  titanic  iron 
partially  decomposed  into  lencoxene,  magnetite,  and  tourmaline. 
No  marked  change  is  visible  in  it  at  tiie  (Ustance  of  lifty  feet 
from  the  line  of  conta-t.  At  twenty-five  feet  the  schists  are 
more  delinitely  and  coarsely  crystalline,  biotite  becomes  more 
prominent,  and  tourmaline  crystals  have  i)ecome  very  common. 
At  fifteen  feet  the  rocks  are  still  schistose,  but  much  fractured, 
and  full  of  shining  dots  that  indicate  a  new  crystallization. 
Here  the  rock  is  a  mica  schist.  The  chlorite  decreases,  and 
biotite  and  tourmaline  increase,  lietwecn  this  point  and  the 
contact  the  schist  loses  t-ntirely  its  structure,  and  is  alteri'd  into 
a  black  hornstone.  l)r('aking  into  smaller  angular  fragments. 
Ten  feet  from  the  schists  a  (pnditative  reaction  for  lioric  acid 
can  be  obtained. 

Last  of  all  is  a  well  defined  zone,  or  a  dark  gray  mass  lilled 
with  reticulated  black  veins.  Scarcely  noticeable  at  the  toj)  of 
the  mountain,  it  lK'conie>  wide  and  proiiiinciit  Itelow.  Tlie  veins 
divide  and  siilulivide.  giviim'  to  the  whoK'  a  fused,  slaggy  ap- 
pearance. Microscopically  it  is  found  to  l>e  a  iieaily  pure  mix- 
ture of  tourni.'iliue  and  (piarlz. 

Just  l)etweeu  the  tourmaline  veinstone  'And  AUniny  granite  is 
a  breccia,  called  the  -'mixed  zone"  by  Dr.  Ilawes,  varying 
from  one  to  twenty  feet  wide  upon  Mt.  Willard,  but  known  to 


u 


be   much  widor  olscwlicre,  as   upon    iMt.  Tcni,     It  coKsists  of 


fr 


agnients  ot  various  schists,  pieces  ot  a  roreigu  (juaitz  poi- 
phyry.  :!!1  connected  by  the  granitic  material.  The  fehlspar 
crvstiils  iire  aii  Itroken  to  fragments  and  the  whoh'  mass  is  im- 
pregnated witli  tourmaline. 

Summarized,  tliese  zones  may  be  thus  stated  :  1.  Zone  of  the 
argillitic  mica  chloritic  schist,  containing  by  actunl  nnalysis 
from  ;ir>  to  .■)ll  pel'  cent,  of  (piartz.  II  to  ID  per  cent,  of  miisco- 
vite.  no  biotite,  -S  to  !;>  percent,  of  clilorite.  "i  i)i'r  cent,  each 
of  titanic  and  magiu'tic  iron,  and  no  tourmabne.  2.  Zone  of 
the  biotitic  mica  sciiist.  ccjutaiuing  \'>  per  cent,  of  quartz,  4:5  of 
botli  mi-'as,  (>  of  chlorite,  and  :>  of  the  iron  oxyds.  ;>.  Zone  of  the 
toui'maline  hornstone.  containing  .')()  per  cent,  of  ((Uartz,  21)  of 
the  micMs.  no  ciilorile.  1  of  tiie  iron  oxyds,  1.")  of  toui'maline. 
4.  Zone  of  the  tounnaliiu'  veinstone,  containing  .")0  per  cent,  of 
quartz,  no  mica  or  chlorite,  ."i  per  cent,  of  iron  oxyds,  and  4()  of 
tourmaline.  .">.  Zone  of  the  mixed  sciiists  and  granite,  (i.  Zone 
of  the  granite  por[ihyry,  biotitic.  7.  Zone  of  the  Albany  liorn- 
blendic  graniti'. 

There  seems  to  be  a  systematic  and  progressive  series  of 
changes  in  the  schists.  First,  water  lasbeen  removed  ;  second, 
boric  acid  and  silica  have  been  added  :  tliird,  alkalies  have  been 
added  directly  upon  the  contact.  These  additions  and  changes 
are  such  as  would  come  from  igneous  eriqitions.  and  theri-fore 
the  inference  is  nuthorized  that  the  Albany  granite  was  eruptive 
like  lava.  The  inclusion  of  varied  products  in  the  mixed  zone 
indicates  the  movement  of  a  lluid  mass  no  inconsiderable  dis- 
tance through  lissures.  Very  hot  vapors  must  have  accomi)a- 
nied  the  eriqttion. 

Such  is  a  brief  sunnnary  of  the  paper  of  the  late  Dr.  Ilawes, 
formerly  assistant  upon  the  (ieological  Survey  of  New  Hamp- 
shire, published  in  the  .!///''/'/>«?(  Jourmil  of  iScioux'  ldkI  ^Irts, 
in  Januarv,  bSMl . 


JIT.    ASCL'TNKY    GW.VXrrK. 


rpon  V  we  have  delineated  two  peaks  of  granite  or  syenite 
known  as  :Mt.  Asciilney  and  Little  Asciitney.  The  igneous  rock 
seems  to  have  been   erui)ted  from  below  through  one  or  more 


I 


'  '■    t 


ven<-s  and  siM-eaO.  over  the  rock  adjiieent,  very  much  in  the  man- 
ner of  modern  lava. 

The  summit  of  Aseiitiiey  lies  near  the  south-east  corner  of 
"Windsor,  })ut  i)ortions  of  the  mass  are  situated  in  the  towns  of 
West  Windsor  and  Weathersfield.  If  the  two  mountains  were 
just  alike,  the  granitic  area,  when  i)rotracted  upon  a  m:ip,  would 
resemble  a  pair  of  spectacles  ;— as  it  is,  the  eastern  higher  area 
is  four  and  a  half  miles  long,  two  and  one  eighth  wide,  and  the 
sunnnit  ;5,1'S()  feet  above  sea  level,  while  the  base  of  the  cone  is 
1,200  feet  above  the  sea.  The  western  area  is  nearly  circular, 
a  mile  and  one  fourth  in  diameter,  and  1,700  feet  above  the  sea. 
The  rock  is  often  a  hornblende  granite — mica  not  being  exclud- 
ed—and the  variety  called  ijranitdl  by  Dr.  llawes,  eontaining 
neitluM-  of  the  accessory  minerals,  is  abundant  in  irregidar 
patches  in  every  part  of  the  cones.  IJrecciated  masses  conqiosed 
of  the  underlying  stratitied  rocks  are  plentiful  upon  the  west 
side  of  the  larger  mass  and  upon  the  smaller  mountaiu.  inso- 
much that  one  can  easily  lielieve  i)(,>rtions  of  the  granite  have 
been  made  from  the  melting  ilown  of  the  fragments.  The  major 
axis  of  the  '•  spectacles  is  six  and  one  half  miles  long,  at  right 
auoles  to  the  course  of  the  strata.  Two  stratilied  groups  under- 
lie the  unstratitied  area.  :Most  of  the  eastern  cone  is  located 
upon  the  calcitVrous  mica  schist.  The  rest  of  it.  and  the  smaller 
cone,  rests  upon  gueiss.  The  gneiss  underlies  the  mica,  schist  at 
the  same  angle  of  dip,  and  we  do  not  yet  discover  any  strati- 
graiihical  axes  in  the  latter.  The  relations  of  all  these  rocks 
ai)pear  upon  section  \ .  This  granite  seems  to  occupy  a  posi- 
tion similar  to  that  of  the  gui'issic  antit'lii\als  in  (ruilford,  1,  and 
Brattleboro',  II,  or  lUack  ^Mountain  in  Duunnerston. 

There  is  no  evidence  of  elevation  of  th"  schists,  in  conse(pience 
of  a  disturbiuice,  when  tlie  igneous  mass  cann'  up.  The  same 
local  variations  api)ear  upon  the  south  that  are  visible  at  the 
north  sides  of  the  mountains.  The  mica  schists  nnmifest  the 
presence  of  heat  for  a  ilistauce  of  ;"iOO  feet  or  more  from  the 
oranite.  The  slates  have  lieeu  indurated  so  that  thev  ring  like 
iron  when  struck  l>y  a  hauiiner.  The  liuiestones  are  sometimes 
calcined,  and  even  gia/.ed.  \'eins  enter  both  the  rocks  from  the 
granite  for  several  yards  distance.  The  gneiss  is  not  altered  at 
the  contact  line.     It  would  seem,  therefore,  as  if  we  had  here 


I 


2$ 


examples  of  contact-phenomena,  and  only  the  later  strata  are 
aft'ected,  because  the  iineiss  had  already  lieen  made  crystalline 
before  the  eruption  of  the  granite. 

The  adjacent  hill-tops  of  the  mica  schist  country  are  approxi- 
mately 1.200  feet  above  the  sea.  which  corresponds  with  the 
elevation  of  the  base  of  the  granite.  On  entering  the  valleys  of 
erosion  at  the  base  of  the  granite,  where  small  streams  have  re- 
mov(>d  considerable  rock,  it  is  discovered  that  the  schists  run  under 
the  igneous  rock,  certainly  for  -'^00  feet.  Were  a  tunnel  driven 
through  the  mountain,  as  through  the  celebrated  Kammorburg 
of  Hohemia,  similar  phenomena  would  be  found  ; — below  a  cer- 
tain horizon— say  1,200  feet— only  the  schists  would  be  cut 
through,  excepting  the  central  plug  of  granite.  The  cone  of 
granite  has  its  base  upon  the  floor  of  schists,  while  its  height  is 
about  2.000  feet.  It  is  to  be  regarded  as  an  overflow  of  igneous 
matter  upon  the  common  rock  of  tlie  neig!il)orhood,  and  where 
.0  comes  in  contact  with  clayey  layers  they  were  baked  ;  and 
where  limestones  were  heated,  the  result  was  calcination,  indu- 
ration, and  glazing.  Ui)on  this  view  it  is  easy  to  understand 
why  there  should  be  an  indurated  belt  about  AOO  feet  in  width 
enveloping  the  cone.  Tiie  heated  mass  covered  the  surround- 
ing country  just  so  far,  anil  Miat  outer  shell  has  since  been 
removed  by  denudation. 

:My  father,  in  the  (Geological  Keport  of  Vermont,  advocated 
the  doctrine  of  the  derivation  of  the  granite  from  below,  l)ut 
supi)Osed  the  cone  continued  to  I'ularge  below  the  surface,  and, 
as  he  conceived  of  it  as  a  liquid,  suggested  its  enclosure  by  walls 
of  schist  which  have  subsequently  been  rtunoved  by  erosion. 
The  prevailing  modern  view  of  tlu'  origin  of  granite  is  like  this, 
except  that  it  demands  a  greater  degree  of  erosion.  Says  Prof. 
J.  W.  Judd,  in  his  work  on  volcanoes.  1S,S1,  p.  2r)2,— '•  The 
plutonic  rucks,  as  we  luu-e  already  seen,  exiiibit  sullieient  proofs 
in  tlieir  liighly  crystalline  character,  and  in  their  cavities  con- 
taining water,  litiueiled  car! ionic  acid,  and  other  volatile  sul)- 
stances,  that  they  nuist  iiave  been  formed  by  tiie  very  slow  con- 
solidation of  igneous  materials  under  enormous  pressure.  Great 
pressures,  it  is  evident,  could  only  exist  at  great  depths  beneath 
the  earth's  surface.  ]\[r.  Sorl>y  and  others  have  endeavored  to 
calculate  what  was   the  actual    thickness  of  rock   under  which 


^  iV 


27 


A- 


certain  granites  must  have  boon  formed,  by  nieasurino;  the 
amount  of  contraction  intlie  liquids  which  liavo  boon  imprisoned 
in  tlio  crystals  of  these  rocks.  The  conclusions  arrived  at  are 
of  a  sutilciently  startlinn;  ciiMracter.  It  is  inferred  that  the 
o-runites  which  have  boon  thus  examined  nuist  have  consolidated 
at  depths  varying  from  00,000  to  80,000  feet  beneath  the  earth's 

surface,"  etc. 

If  Ascutney  were  the  only  granite  mountain  in  New  England, 
it  might  be  easy  to  imagine  an  erosion  of  from  20. 000  to  70,(»<»0 
feet  from  around  it ;  but  what  is  true  of  this  mountain  must 
have  been  true  of  all  New  England  and  of  the  whole  crystalline 
area  of  the  Atlantic  coast.  A  tract  of  country,  say  1 ,000  miles 
long  and  ;^00  miles  wide,  according  to  this  view,  has  been  cov- 
ered bv  rock  from  fotn-  to  fourteen  miles  in  thickness,  which 
has  been  transitorted  by  streams  of  water  oceanward.  If  that 
were  true,  t)<en  our  Atlantic  coast  line  would  have  been  several  ,^y-  ^' 
hundred  miles  nearer  the  old  world  than  it  is  now. 

Such    extreme  views   are   entirely  unnecessary.     Two   other 
agencies   may  be  called   upon,  besides  the  weight  of  overlying 
rock— lateral  pressure   and  elastic  vapor  held   ii     confinement. 
Or,  if  it  be  necessary  to  believe  that  the  liiiuids   condensed  so 
far  below  the  surface,  the  igneous  mass  may  have  Howod  through 
fissures  witiiout  losing  its  inclusions,  and  kept  thom  intact  till 
within  a  few  hundred^  feet  of  the  light.     If  slides  prepared  for 
the  microsooi.o  can  iiold  drops  of  liriuid  carbonic  acid  restrained 
by  the  twentieth  part  of  an   incii  of  rock-wall,  why  could  not 
several  hundred  feet  of  pasty  cooling  lava  bo  eciually  eftectual? 
At  the  surface  the  inclusions  nnist  have  escaped  into  the  atmos- 
phere just  as.   upon  stream  sof  niodorn   lava,  steam  and  vapors 
boil  aiid  disappear.     After  solidification,   all  those  imprisoned 
vapors  are  tinnly  enclosed  wiiother  within  ten  feet  or  ten  miles 
of  rock.     The  original   -urface,  i\ow  deiuidod,  may  have  been  a 
genuine  lava.     Some  modern  lavas,  like  granites,  contain  inclu- 
sions of  condensed  gasos.  and   present  many  of  the  phenomena 
characteristic  of  the  oldor  rock;  yet  no  one  supposes  that  five 
or  ton  miles  of  rock  has  boon   romovcd  from  above  them.     The 
conditions  of  niodorn   aipioo-igneous  lava  fusion   are  not  very 
different  from  those  invoked  for  the  origin  of  granite. 

It  is  easy  to  name  other  mountains  of  granite  and  i)ori)hyry, 


,» 


.V 


28 


which  so  resemble  Ascutuey  as  to  make  one  believe  the}'  will 
present  evidences  of  a  similar  origin.  Such  may  be  found  upon 
our  sections, — as  Moose  Mountain  near  the  east  end  of  V  ; 
Green  Mountain,  Kdingluim,  and  the  Ossipee  Mountains  in  V' I ; 
Pequawket  in  YlII  ;  and  Star  King,  near  Jefferson,  in  IX. 
There  are  many  others  in  tlie  Wliite  Mountains. 

Another  class  of  volcanic  ejections,  probably  older  than  the 
granites  of  the  White  Mountains,  are  largely  developed  upon 
sections  XI  to  XIII  in  Vermont.  Tiie  rocks  are  referred  to  the 
Huronian  in  our  descriptions,  and  consist  of  stratitied  diabsises, 
protogenes,  epidotic  and  chloritic  scliists,  fine-grained  quartzites, 
etc.  It  is  su|)posed  they  may  have  been  metamorphosed  from 
volcanic  ashes  and  scoritt.  Some  of  the  mountains  exhibit 
dome-shaped  features,  and  thei^fore  resemble  volcanic  piles 
much  degraded.  Selwyn  calls  the  extension  of  these  rocks  into 
Canada  the  "Volcanic  group."  and  was  the  first  person  to  call 
attention  to  their  reseml)Iance  to  rocks  of  igneous  origin  in 
Great  Britain  and  Australia.  These  views  will  commend  tliem- 
selves  to  those  who  are  familiar  with  the  lithological  character 
of  igneous  rocks. 

EARLY   HISTOIiY    OF   TiIK    CONTINENT. 

In  the  geology  of  New  Hampshire  I  have  shown  how  the  dry 
land  of  the  state  has  been  gradually  reclaimed  from  the  primi- 
tive ocean,  and  that  the  earliest  islands  can  now  be  recognized  in 
the  several  porfihyritic  gneiss  areas.  I  have  lately  gone  further, 
and  argued  tliat  tliese  same  areas,  with  others  like  them,  re|)re- 
sented  liie  lirst  dry  land  of  the  whole  American  continent.  It 
is  claimed  tliat  they  were  of  eruptive  origin,  very  much  like  sub- 
marine volcanoes,  and  that  they  gradually  gathered  sediment 
from  the  wash  of  the  hills,  and  increased  in  size  on  account  of 
general  continental  elevation.  Some  of  the  conclusions  were 
suggested  by  a  personal  study  of  the  Hawaiian  islands.  A  few 
of  the  considerations  favoring  our  theory  will  now  be  presented. 

1.  Considering  the  igneous  origin  of  tlie  earth,  volcanic  ener- 
gies would  naturally  continue  their  action  as  soon  as  there  was 
a  crust  to  be  broken  through,  and  immense  piles  of  melted  rock 
would  ooze  from  the  numerous  fissures.  Up  to  Laurentiau 
times  all  admit  the  universalitv  of  igneous  outflow,  while  but  few 


I  { 


29 


h 


V 


have  ventured  to  speak  of  anything  like  volcfvnic  action,  except 
as  it  has  been  manifested  in  the  formation  of  dikes  in  these 
early  periods.  There  lias  been  a  tendency  to  class  tlie  ancient 
granites  and  porphyries  with  rocks  of  sedimentary  origin,  and 
conse(piently  to  restrict  the  action  of  igneous  agencies  to  phe- 
nomena of  sligiit  importance.  Several  English  writers,  and,  in 
our  country,  Dr.  Selwyn,  of  Canada,  have  been  calling  our  at- 
tention to  the  existence  of  a  volcanic  group  in  later  Huronian 
or  early  Cambrian  times.  These  are  the  rocks  so  largely  devel- 
oped about  Lake  Superior,  New  England,  and  the  Province  of 
Quebec,  consisting  of  stratified  schists,  diorites,  diabases, 
araygdaloids,  and  felsites,  identical  in  composition  with  true 
eruptive  masses  of  the  same  name.  Investigation  shows  that 
oftentimes  tliese  schists  are  disposed  like  the  lavas  ejected  from 
one  series  of  volcanic  vents.  Suppose,  for  exami)le,  that  Etna 
or  Vesuvius  should  become  extinct :  in  the  course  of  ages  the 
rains  would  obliterate  the  craters,  and  reduce  the  lavas  to  a 
rounded  dome  of  greater  or  less  regularity.  We  should  recog- 
nize the  volcanic  origin  of  the  mountain  in  the  absence  of  cra- 
ters, from  the  lithological  similarity  of  tlie  rocks  to  those  known 
to  have  been  melted  and  ejected  from  vents,  while  the  disposal 
of  the  material  in  a  conical  attitude  shows  us  that  it  might  once 
have  been  protruded  from  below.  So  we  find  in  our  Eastern 
country  many  domes  of  diabasic  or  protogenic  schists,  whose 
volcanic  origin  may  be  predicated,  both  from  their  lithological 
character  and  physical  aspect. 

Now  this  volcanic  group  of  Huronian  times  indicates  the  ex- 
istence of  a  greater  degree  of  igneous  activity  than  has  been 
described  for  the  palezoic  ages,  even  in  Great  Britain  ;  and  con- 
sequently this  is  an  indication  pointing  significantly  towards  the 
predominance  of  thermal  influences  in  the  still  earlier  periods. 
In  the  Laurentian  age  the  fires  sliould  have  been  yet  more  vigor- 
ous, because  the  time  of  universal  igneous  fluidity  was  less  re- 
mote. 

2.  A  careful  study  of  the  crystalline  rocks  of  the  Atlantic 
slope  indicates  the  presence  of  scattered  ovoidal  areas  of  Lau- 
rentian gneisses.  Those  best  known  have  been  descril)ed  in  the 
Geology  of  New  Hami)shire.  Instead  of  a  few  large  synclinal 
troughs  filled  to  great  depths  with  sediments,  the  okbst  group 


80 


is  disposed  in  no  less  tlian  twenty-two  sirens  of  small  size,  scat- 
tered like  the  islands  in  an  arcliipelago.  In  a  chapter  upon  the 
physical  history  of  tlie  slate,  I  have  proposed  llie  tlieory  that 
the  earliest  land  within  its  limits  consisted  of  this  series  of 
islands,  not  packed  together  as  closely  as  now,  in  an  area  of  per- 
haps three  thousand  live  lumdred  scptare  miles,  hut  as  much 
more  widely  separated  as  would  be  determined  by  smoothing 
out  the  various  antielinals  and  vrelinals  that  were  formed  later. 
Bv  reference  to  <tur  maps  in  Ma'?;  ',  ]Massachusetts,  New  Jersey, 
Pennsylvania,  N'irginia,  North  Carolina,  and  (ieorgia,  many  sim- 
ilar ovoidal  Laurentian  ai'eas  may  be  specified,  usually  larger 
than  tiiose  of  New  Hampshire.  This  may  bo  due  partly  to  a 
less  thorougli  knowledge  of  the  exact  areas  occu[)ied  l)y  this 
older  gneiss,  and  partly  to  the  existence  of  a  greater  number  of 
volcanic  vents,  giving  rise  to  a  more  widely  si)read  and  thicker 
mass  of  ejected  material.  Over  the  Atlantic  slope  and  Canadian 
highlands  these  primeval  islands  hnve,  in  later  periods,  been 
cemented  together  by  a  subse(iuent  dei)osition  of  material ;  but 
in  Missouri,  Arkansas,  and  Texas  we  recognize,  even  now,  these 
early  islands. 

3.  The  lithoU)gy  of  the  Laurentian  and  other  crystalline  rocks 
is  very  like  that  of  igneous  ejections.  We  now  divide  the  Lau- 
rentian into  three  parts.  First  and  lowest  is  the  porphyritic  gneiss 
of  New  ILunpshire  corresi)onding  to  Selwyn's  proposed  restric 
tion  of  the  whole  series  to  "  all  those  clearly  lower,  vuiconform 
able,  granitoid,  or  syenitic  gneisses  in  which  we  never  lind  inter- 
stratitied  bands  of  calcareous,  argillaceous,  arenaceous,  and 
conglomeratic  rocks."  Next  will  follow  the  Hastings  and 
Grenville  series,  and  all  the  schists  containing  the  Eozoon, 
as  well  as  the  Bethlehem,  Lake  Winnipiseogee,  and  Mont- 
alban  groups  of  the  Atlantic  slope.  Tiiird,  will  follow  the 
Montalban  ;  while  the  Labrador  or  Norian  series,  sometimes 
called  Upper  Laurentian,  is  rejected  since  it  is  an  igneous 
rock,  not  stratified.  The  lower  Laurentian  is  azoic,  the  other 
wroups  eozoic  ;  and  unless  newer  distinctions  are  to  be  made 
hereafter,  it  looks  as  if  we  might  claim  these  various  azoic 
Laurentian  islands  as  the  first-formed  dry  land,  as  they  cer- 
tainly are  the  nuclei  of  the  existing  continents. 

There  are  no  minerals  in  these  Laurentian  islands  that  do  not 


31 


•I 


occur  ill  eruptive  siratiite  ;  and  the  scliistose  structure  is  often  so 
fiiint  that  the  field  geoloi>;ist  need  not  1)0  blamed  if  he  acknowl- 
ed<>es  his  inability  to  detect  it.  Likewise  we  discover  the  same 
fluidiil  inclusions  and  the  vacuoles  that  pertain  to  granite.  If  we 
should  follow  Sorbv  and  Clifton  Ward  in  saying  that  granite  has 
been  formed  beneath  a  pressure  equivalent  to  a  weight  of  forty 
thousand  feet  of  strata,  the  same  must  bo  said  of  the  early 
gn-'isses.  With  this  general  assertion  of  the  identity  of  gneiss 
and  eruptive  granite  we  must  be  satisfied  at  present,  without 
entering  into  detail. 

4.  The  tvualogy  of  the  origin  of  oceanic  islands  at  the  present 
day  suggests  the  igneous  derivation  of  the  I^aurentian  areas. 
Most  of  the  high  islands  of  the  Pacilic  are  com|)osed  of  lava, 
with  the  volcanoes  frequently  in  action. 

The  so-called  lowlands  are  likewise  of  volcanic  t>rigin, — since 
coral  polyps  have  l)uilt  up  roofs  upon  the  igneous  area  after  the 
disappearance  of  the  fire,  and  the  Hawaiian  areas  are  encircled 
by  roefs.  After  the  volcanoes  have  l)ecome  cold,  loose  material 
would  be  worked  in  between  them,  coral  roefs  would  grow,  and 
in  various  ways  the  land  area  would  lio  cnlai'ged,  and  finally  an 
archipelago  may  become  a  large  island.  It  needs  only  time  and 
a  rei)etition  of  these  constructive  agencies  to  make  a  continent 
out  of  a  series  of  archipelagoes. 

5.  The  oceanic  volcanic  islands  are  not  inferioi  in  size  to  the 
crystalline  Laurentian  areas  upon  the  present  continents. 
Hawaii,  of  the  Hawaiian  group,  may  illustrate  their  position  and 
shape.  Its  area  above  the  water-line  is  4,210  square  miles,  and 
its  cubical  contents  above  the  sea-level  are  about  the  same 
with  those  of  New  IIanii)shiro.  It  rises  from  a  plateau  over 
1(5,000  feet  deep,  thus  forming  a  cone  30.000  f-jt  high,  whose 
cubical  contents  must  be  twenty  times  greater  than  the  [jortion 
making  dry  land.  The  length  of  the  entire  series  of  islands,  all 
of  similar  character,  is  350  miles,  and  the  area  of  the  base  of  the 
lava  must  be  about  100,000  s(iuare  miles.  These  cones  have 
been  built  up  by  the  accumulation  of  lava  ejected  from  the  in- 
terior of  the  earth,  and  thoy  are  entirely  isolated,  the  nearest 
land  being  one  thousand  miles  distant.  The  ground-plan  of 
this  volcanic  mass  is  that  of  two  elliptical  areas,  either  of  which 
is  l.ke  some  of  our  Laurentian  islands,  and  is  certainly  as  large 


82 


as  any  of  those  tiiiclont  lands  south  of  the  St.  Lawrence.  The 
hind  !uva  of  the  Hawaiian  ishinds  is  less  than  that  of  Massachu- 
setts. l)nt  their  base  must  l)e  etiual  to  the  whole  of  New  Kn<;jland 
and  New  York  conihined.  Surely  it  cannot  be  avowed  that  vol- 
canic areas  a  e  too  small  to  be  compared  with  the  space  occu- 
pied by  our  oldest  formation 


TIITCKNESS  OF  THE  FORMATIONS. 

For  a  thousand  furtiier  details  the  reader  is  referred  to  the 
published  and  manuscrii)t  sections  and  catalogue,  accessible  to 
all  in([uirer3  at  the  Museum.  I  will  close  by  adding  a  list  of  the 
several  formations  of  New  Hampshire  and  Vermont  in  their  sup- 
posed natural  order,  with  their  estimated  thickness : 

FEET. 

Devonian  Helderberg,  near  Memphremagog  lake,  .         .         200 
Niagara  group,  at  Littleton,  etc.,  ....         500 

CHAMPLAIN    VALLEY. 

Loraine  slate,       ..... 
Hydro-mica  schist  (Tacouic  range), 
Trenton  limestone,        .... 
Black  river  and  Birdseye  limestone, 
Chazy  limestone,  .... 

Levis  limestone,  ..... 
Upper  calciferous  sandroek. 
Lower  "  '^  .         .         . 

Fucoidal  layer,     ..... 
Potsdam  sandstone,  red, 

"  ''  gray,     . 

"  "  quartzite, 

Georgia  slates,      ..... 
Cambrian  slates  and  schists, 

Total  of  Champlain  Valley, 

CRYSTALLINE    GROUPS. 

Calciferous  mica  schist  and  Coos  group,  . 
Ivearsarge  group,  ..... 
Uockingham  mica  schist, 


.   2,000 

400  to  GOO 

40 

400 

000 

200 

400 

200 

500 

.  310 

.  1,200  1,200 

.   3,000 

.   4,000 

13,740 


12,000 

i,3or 

6,000 


88 


400 

2,000 

o  GOO 

40 

400 

000 

200 

400 

200 


Merrimack  group,    .... 
i  !iironiiiii,        ..... 
n()riil)lcn(U'  schist,  .... 
I'ppcr  Liuirentiaii,  MoiiL-ilhan, 
Middle  Laurentian,  Lake  VVimiipiseogee 

Mountain)  gneiss, 
Middle  Laurentian,  licthlehem  gneiss, 
Lower  Laurentian,  I'orpliyritic  gneiss. 


Total  crystalline, 


Grand  total. 


•              •              • 

4,;ioo 

•                •                • 

12.000 

•                •                • 

l.ftOO 

•               • 

10,000 

((ireen 

•          •          • 

is.noo 

•         •          • 

t;,;5oo 

•          •          ■ 

5,000 

•         t         • 

77,000 

•         •         • 

!)0,740 

I 


